The BSD109A is a bi-polar stepper driver board using the new Bigfoot profile which is twice the size of the regular pololu style drivers used in 3D printers and CNCs. The BSD109A is controlled using Step and Direction signals from a micro controller. Current is set by either using the on-board trimmer or the Vref pin for digital pot control if supported by host controller board.

This driver chip utilizes a feature called ADMD (Advanced Dynamic Mixed Decay) which allows the motors to run quieter and jitter-free.